Method and apparatus for managing control channel in a mobile communication system using mulitiple antennas

ABSTRACT

Methods and apparatuses are provided for receiving control information by a terminal. A control channel message is received on a control channel. Control information comprising a transmission rank and precoding matrix information is extracted from the control channel message if a common pilot is used for data demodulation. The control information comprising the transmission rank and information about a dedicated pilot is extracted from the control channel message if the dedicated pilot is used for the data demodulation.

PRIORITY

This application is a Continuation of Application of U.S. patentapplication Ser. No. 14/864,320, filed in the U.S. Patent and TrademarkOffice (USPTO) on Sep. 24, 2015, which is a Continuation Application ofU.S. patent application Ser. No. 14/325,995, filed in the USPTO on Jul.8, 2014, now U.S. Pat. No. 9,312,936, issued on Apr. 12, 2016, which isa Continuation Application of U.S. patent application Ser. No.12/013,711, filed in the USPTO on Jan. 14, 2008, now U.S. Pat. No.8,774,152, issued on Jul. 8, 2014, which claims priority under 35 U.S.C.§119(a) to a Korean Patent Application filed in the Korean IntellectualProperty Office on Jan. 12, 2007 and assigned Serial No.10-2007-0003579, the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to a method and apparatus formanaging forward control channels in a mobile communication system, andmore particularly, to a method and apparatus for transmitting/receivingdata over a Forward Shared Control Channel (F-SCCH), adapted to supportvarious antenna technologies for data transmission in a forward link ofa mobile communication system using multiple transmit/receive antennas.

2. Description of the Related Art

The mobile communication system has evolved into a high-speed,high-quality wireless packet data communication system that providesdata services and multimedia services in addition to the earlyvoice-oriented services. Recently, various mobile communicationstandards, such as High Speed Downlink Packet Access (HSDPA) and HighSpeed Uplink Packet Access (HSUPA), both defined in 3^(rd) GenerationPartnership Project (3GPP), High Rate Packet Data (HRPD) defined in3^(rd) Generation Partnership Project-2 (3GPP2), and IEEE 802.16, havebeen developed to support the high-speed, high-quality wireless packetdata communication services.

The existing 3^(rd) Generation wireless packet data communicationsystems, such as HSDPA, HSUPA and HRPD, use technologies of an AdaptiveModulation and Coding (AMC) method and a channel-sensitive schedulingmethod to improve the transmission efficiency.

With the use of the AMC method, a transmitter can adjust the amount oftransmission data according to the channel state. That is, when thechannel state is not ‘Good’, the transmitter reduces the amount oftransmission data to adjust the reception error rate to a desired level,and when the channel state is ‘Good’, the transmitter increases theamount of transmission data to adjust the reception error rate to thedesired level and to efficiently transmit a large volume of information.

With the use of the channel-sensitive scheduling-based resourcemanagement method, the transmitter selectively services the user havinga good channel state among several users, thus increasing the systemcapacity compared to the method of assigning a channel to one user andservicing the user with the assigned channel.

The capacity increase is referred to as ‘multi-user diversity gain’. Insum, the AMC method and the channel-sensitive scheduling method aremethods of applying the appropriate modulation and coding techniques atthe most-efficient time determined depending on the partial channelstate information fed back from a receiver.

To realize the AMC method and the channel-sensitive scheduling method,the receiver should feed back the channel state information to thetransmitter. The channel state information that the receiver feeds backin this way is referred to herein as a ‘Channel Quality Indicator(CQI)’.

Recently, intensive research has been conducted to replace Code DivisionMultiple Access (CDMA), the multiple access scheme used in the 2^(nd)and 3^(rd) generation mobile communication systems, with OrthogonalFrequency Division Multiple Access (OFDMA) in the next generationsystem. 3GPP and 3GPP2 have started their standardizations on theevolved systems employing OFDMA. It is generally known that the OFDMAscheme, compared to the CDMA scheme, can expect the capacity increase.One of the several causes bringing about the capacity increase in theOFDMA scheme is that the OFDMA scheme can perform scheduling in thefrequency domain (Frequency Domain Scheduling). As though thetransceiver acquires capacity gain according to the time-varying channelcharacteristic using the channel-sensitive scheduling method, thetransceiver can obtain the higher capacity gain with use of thefrequency-varying channel characteristic. However, to support thefrequency domain scheduling, the transmitter should previously acquirechannel state information separately for each frequency. That is, thetransmitter needs CQI feedback information for each frequency, causingan increase in the load due to the CQI feedback transmission.

In the next generation system, intensive research is being conducted onthe introduction of Multiple Input Multiple Output (MIMO) technologyemploying multiple transmit/receive antennas. The term ‘MIMO’ as usedherein refers to a technology that simultaneously transmits multipledata streams over the same resources using multiple transmit/receiveantennas. It is well known that when the channel state is ‘Good,’ it ispossible to increase the throughput at the same error rate bytransmitting multiple low-modulation order data streams rather thanincreasing the modulation order. In the MIMO technique, the dimensionover which an individual data stream is transmitted is referred to as a‘layer’, and the method that applies AMC separately according to thechannel state of the layer is efficient in increasing the capacity. Forexample, Per Antenna Rate Control (PARC) is a technology in which everytransmit antenna transmits a different data stream, and in thistechnology, the layer is a transmit antenna. The multiple transmitantennas experience different channels, and the PARC technique appliesAMC such that a larger amount of data can be transmitted via thetransmit antenna having a good channel state and a less amount of datacan be transmitted via the transmit antenna having a poor channel state.As another example, in Per Common Basis Rate Control (PCBRC) the layeris a fixed transmission beam. Therefore, the PCBRC technique transmits agreater amount of data over the transmission beam with a good channelstate, and transmits a less amount of data over the transmission beamwith a poor channel state.

Commonly, the packet mobile communication system using multiple antennastransmits/receives control information using a Forward Shared ControlChannel (F-SCCH). The F-SCCH is a channel transmitted along with thetransmission data when data is transmitted to an arbitrary terminal atan arbitrary time, and this channel is characterized by including thecontrol information necessary for demodulation of the transmission data.Using Table 1 below, the constituent fields of F-SCCH will beconsidered. Table 1 shows a message format of the shared controlchannel, and the message is transmitted over the shared control channel.Besides the fields defined in Table 1, other fields used for performingother functions can be added to the shared control channel, and/or thenumber of bits used for expressing each of the fields is subject tochange.

TABLE 1 Field Block type MACID Persistent ChanID PF Ext. TX Rank # bits2 9-11 1 6-8 4-6 1 2 FLAM 00 1 1 1 1 1 0 MCW 01 1 1 1 1 1 0 FLAM1 MCW 101 0 0 3 1 0 FLAM2 SCW 11 1 1 1 1 1 1 FLAM

Referring to Table 1, ‘Block type’ is a field indicating a type of themessage. ‘MAC ID’ is a field indicating an identifier (ID) of aterminal. That is, after receiving a shared control channel, theterminal checks MAC ID included in the received shared control channelto determine whether the received MAC ID is equal to a MAC ID previouslyagreed upon between the terminal and a base station, and thus determineswhether there is any data being transmitted to the terminal itself.Although the MAC ID is included in the message of the shared controlchannel in Table 1, by way of example, the MAC ID can also betransmitted by scrambling the message of the shared control channelusing a MAC ID-specific scrambling sequence of the target user. A‘Persistent’ field is a field indicating whether the resource assignedto the terminal itself is persistent resource or non-persistentresource.

‘Channel Identifier (ChanID)’ is a field indicating an identifier forthe assigned resource. ‘Packet Format (PF)’ is a field for notifying amodulation order, such as QPSK, 8PSK and 16QAM, used for datatransmission, and a code rate. ‘Extended Transmission (Ext. Tx)’ isinformation indicating a time length of transmission data. ‘Rank’indicates the number of data streams transmitted via multiple antennas.‘Forward Link Assignment Message (FLAM)’ indicates that the message is amessage for resource assignment for the forward link.

‘Multi CodeWord (MCW)’ indicates that when multiple data streams aretransmitted via multiple antennas, the multiple data streams are streamsthat have undergone channel coding (for example, turbo coding)independently of each other. ‘Single CodeWord (SCW)’ indicates that whenmultiple data streams are transmitted via multiple antennas, themultiple data streams are parts of one codeword that has undergonechannel coding.

In Table 1, numerals shown in the shaded blocks indicate whether each ofthe message types include a particular field. For example, FLAM has aRank field=0, but SCW FLAM includes the Rank field. This means that theFLAM, as it is a message type used for Single Input Multiple Output(SIMO) transmission, does not need the Rank field used for transmissionof multiple data streams, whereas the SCW FLAM needs the Rankinformation as multiple data streams can be transmitted.

However, the message format of the foregoing conventional shared controlchannel does not support precoding and/or various types of pilotpatterns. When a common pilot is used, it is necessary to separatelynotify which precoding is applied thereto, because the pilot has notundergone precoding. However, when a dedicated pilot is used, it isnecessary to separately notify which pilot pattern is used therefor. Theconventional technology, however, gives no definition of the field fornotifying such information.

SUMMARY OF THE INVENTION

The present invention has been made to address at least the aboveproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the present inventionprovides a data transmission/reception method and apparatus forsupporting various pilot patterns in a mobile communication system usingmultiple antennas.

Another aspect of the present invention provides a method and apparatuscapable of efficiently managing control channels in a mobilecommunication system using multiple antennas.

According to one aspect of the present invention, a method is providedfor receiving control information by a terminal. A control channelmessage is received on a control channel. Control information comprisinga transmission rank and precoding matrix information is extracted fromthe control channel message if a common pilot is used for datademodulation. The control information comprising the transmission rankand information about a dedicated pilot is extracted from the controlchannel message if the dedicated pilot is used for the datademodulation.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a diagram illustrating a structure of an SCW MIMO transceiver,according to an embodiment of the present invention;

FIG. 2 is a diagram illustrating a structure of an MCW MIMO transceiver,according to an embodiment of the present invention;

FIG. 3 is a diagram illustrating a structure of an Antenna SelectionSTTD transceiver, according to an embodiment of the present invention;

FIGS. 4 to 6 are flowcharts illustrating a shared control channelinformation writing methodology, according to an embodiment of thepresent invention; and

FIGS. 7 to 10 are flowcharts illustrating a shared control channelinformation analysis methodology, according to an embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention are described in detailwith reference to the annexed drawings. In the drawings, the same orsimilar elements are denoted by the same or similar reference numeralseven though they are depicted in different drawings. Detaileddescriptions of constructions or processes known in the art may beomitted to avoid obscuring the subject matter of the present invention.

The present invention provides a method and apparatus fortransmitting/receiving data using precoding and/or various types ofdedicated pilot patterns in a mobile communication system employingmultiple antennas. To this end, the present invention adds a field of ashared control channel, for MIMO transmission, to transmit/receive dataefficiently.

For a better understanding of the present invention, a description willfirst be made of the system using multiple antennas.

When MIMO is realized with multiple antennas, a precoding method is usedfor adaptively forming transmission beams according to the channelstate. The term ‘precoding’ as used herein refers to an operation inwhich a transmitter pre-distorts transmission signals before the stageof transmitting signals over transmit antennas. If the precoding isrealized with linear combining, the precoding process can be expressedas Equation (1).

x=Es   (1)

In Equation (1), ‘s’ is a K×1 vector, and denotes a desired transmissionsignal, and ‘x’ is an M×1 vector, and denotes an actually transmittedsignal. However, K denotes the number of symbols simultaneouslytransmitted by MIMO over the same resources, and M denotes the number oftransmit antennas. Further, E is an N×K matrix, and denotes precoding.That is, Equation (1) indicates that a MIMO transmitter with M transmitantennas applies a precoding scheme, called E, when it simultaneouslytransmits K signal streams.

A precoding matrix E is adaptively determined according to atransmission MIMO channel. However, when the transmitter cannot acquireinformation on the transmission MIMO channel, it performs precodingaccording to feedback information reported by the receiver. To this end,a precoding codebook including a finite number of precoding matrixes Eis preset between the transmitter and the receiver. The receiver selectsthe precoding matrix E most preferred in the current channel state fromthis precoding codebook, and feeds it back to the transmitter. Then thetransmitter performs MIMO transmission using the precoding matrix.

The transmission signal of Equation (1), received over a MIMO channel H,is expressed as Equation (2).

y=Hx+z=HEs+z   (2)

In Equation (2), y and z each are an N×1 vector, and denote a signal anda noise signal received at N receive antennas, respectively, and H is anN×M matrix, and denotes a MIMO channel. The received signal undergoesreception combining process so that a Signal-to-Interference and NoiseRatio (SINR) of a transmission signal stream of each layer may beimproved. The signal r that underwent the reception combining process isdefined as Equation (3).

r=Wy=WHx+Wz=WHEs+Wz   (3)

In Equation (3), W is an N×N matrix, and denotes the reception combiningprocess, and r is an N×1 signal vector. To correctly receive atransmission signal stream of each layer, it is possible to additionallyuse a reception technique such as interference cancellation and/orMaximum Likelihood (ML) reception.

The MIMO technique can be classified into a Single CodeWord (SCW) schemeand a Multi-CodeWord (MCW) scheme according to the number of codedpackets from which multiple signal streams transmitted by MIMO techniqueare generated.

FIG. 1 illustrates a structure of an SCW MIMO transceiver, according toan embodiment of the present invention. Referring to FIG. 1, a desiredtransmission data stream is converted into one coded packet signalstream after undergoing a channel coding and modulation process at block101. For MIMO transmission, this signal stream is demultiplexed into Ksignal streams at demultiplexer 103. The demultiplexed K signal streamsare linear-converted into M signal streams to be transmitted viaassociated transmit antennas, after undergoing precoding at precoder105. This can be considered a process of transmitting K signal streamsover different transmission beams. The precoded M signal streams aretransmitted via transmit antennas 109 a-109 m by way of associatedtransmission processors 107 a-107 m, respectively. The transmissionprocessors 107 a-107 m each not only generate a CDMA or OFDMA signal,but also filter or Radio Frequency (RF) process at each antenna. Thetransmitted signals are received at N receive antennas 111 a-111 n, andthe signals received at the receive antennas are restored to basebandsignals by means of associated reception processors 113 a-113 n. Thereception-processed signals undergo reception combining at a receptioncombiner 115, and are then restored to the original desired transmissionsignal stream after undergoing multiplexing at multiplexer 117. Finally,the original desired transmission data stream is restored by means ofdemodulation and channel decoding at block 119.

According to the SCW MIMO characteristic, because the SCW MIMOtransmitter generates multiple transmission signal streams by applyingone channel coding and modulation process 101, it only needs to receiveone CQI feedback. However, the number of MIMO-transmitted transmissionsignal streams, i.e., the number K of transmitted MIMO layers, should beadjusted according to the channel state. The number K of transmittedMIMO layers is referred to herein as ‘Rank’. Therefore, the feedback ofSCW MIMO is composed of one CQI representative of the channel state oftransmission MIMO layers, and the number ‘Rank’ of transmission MIMOlayers.

FIG. 2 illustrates a structure of an MCW MIMO transceiver, according toan embodiment of the present invention. The MCW MIMO transceiver, unlikethe SCW MIMO transceiver, transmits different coded packet signalstreams over different MIMO layers. Therefore, a desired transmissiondata stream is demultiplexed into as many streams as ‘Rank’ indemultiplexer 201, and the demultiplexed signal streams are convertedinto signal streams of associated MIMO layers after undergoing differentchannel coding and modulation processes at blocks 101 a-101 k,respectively. The following transmission process is equal to that of theSCW MIMO transceiver described above, and the signals to be transmittedvia M transmit antennas 109 a-109 m are generated by means of theprecoding process at precoder 105 and the transmission processingprocesses of transmission processors 107 a-107 m of their associatedtransmit antennas. A reception process of the MCW MIMO transceiver isalso equal to the reception process of the SCW MIMO transceiver inseveral steps immediately after the signal reception.

The receiver uses an interference canceller 205 in FIG. 2, by way ofexample, however, the receiver can use other types of reception methods.The signals received at N receive antennas 111 a-111 n are restored tothe transmission signals of associated layers after passing throughreception processors 113 a-113 n, and a reception combiner 115 in order.The restored signals include mutual interference. In MCW MIMO, becausethe transmission signals have undergone different channel coding andmodulation processes separately for associated layers, the receiver cancancel the first restored signal of a particular layer to remove theinterference effect that the corresponding signal renders to otherlayers. The use of the interference canceller 205 can improve channelcapacities of the MIMO layers, so it is possible to transmit a largeramount of data through the MCW MIMO transmission. A reception processbased on the interference cancellation will be described below. When asignal of one layer is successfully restored through demodulation andchannel decoding at block 203, the receiver cancels interference usingthe restored signal at interference canceller 205. Theinterference-canceled signal stream 207 is delivered back to thedemodulation and channel decoding process block 203, and the restorationand interference cancellation are repeated until signals of all layersare successfully restored and/or there is no more signal of layer to berestored. Finally, the restored multiple signal streams of associatedlayers are restored to one original desired transmission data stream bymeans of multiplexer 209.

According to the MCW MIMO characteristic, because the MCW MIMOtransmitter generates multiple transmission signal streams by applyingmultiple channel coding and modulation processes in blocks 101 a-101 kseparately for associated layers, it should receive CQI feedbacksseparately for their associated layers. As to the Rank, it can beexpressed in an immanent way by setting a predetermined CQI valueindicating ‘No Transmission’ among CQI values, rather than separatelyfeeding it back. Therefore, the feedback of MCW MIMO is composed ofmultiple CQIs representative of channel states of associatedtransmission MIMO layers.

A method for forming and expressing precoding can be classified into aknockdown method and a ready-made method.

The knockdown method establishes multiple universal matrixes, designatesone of the universal matrixes, and selects certain column vectors of thedesignated universal matrix to make a detailed precoding method. Forexample, when the knockdown method establishes two matrixes U1 and U2 asuniversal matrixes, and selects column vectors #1 and #3 of the matrixU1 to form two layers for MIMO transmission, the precoding matrix isdefined as E=[U1(:,1), U1(:,3)], where A(:,i) denotes an i^(th) columnvector of a matrix A. To express the precoding matrix formed by theknockdown method, MCW MIMO uses a universal matrix index indicatingwhich universal matrix is selected. The selection/non-selection ofcolumn vectors can be expressed by means of a Packet Format of eachlayer. The Packet Format is used for indicating a modulation scheme anda channel coding scheme when AMC is realized, and one of Packet Formatsis set to ‘Null’ to indicate no transmission of data. In this manner,even though the information indicating which column vector is selectedis not provided by a separate scheme, MCW MIMO can distinguish theactivated column vectors from the inactivated column vectors using theNull Packet Format.

In order to express the precoding matrix formed by the knockdown method,SCW MIMO needs not only the universal matrix index but also the vectorbitmap indicating which column vector is selected. As to the vectorbitmap, a bitmap corresponding to a column length of the universalmatrix is established. When an nth bit of the bitmap is set to ‘1’, itindicates that an n^(th) column vector is selected, and when the n^(th)bit is set to ‘0’, it indicates that the n^(th) column vector is notselected.

The ready-made method establishes multiple precoding matrixes andselects one of the precoding matrixes. It is necessary to adjust Rankeven with the ready-made method. While the knockdown method adjusts Rankby designating which column vector of the selected universal matrix isselected, the ready-made method adjusts Rank by designating only theRank value. Once Rank is designated, the ready-made method selects afirst column vector through a (Rank)^(th) column vector of the selectedprecoding matrix. MCW MIMO uses a matrix index for selecting a precodingmatrix in order to express the precoding matrix formed by the ready-mademethod. SCW MIMO uses a matrix index and a Rank value to express theprecoding matrix formed by the ready-made method.

One example of the simple precoding methods based on the knockdownmethod can include binary unitary precoding for Antenna Selection MIMO.For the universal matrix defined by the knockdown method, only oneidentity matrix I is defined. The identity matrix is a matrix in whichall diagonal components are ‘1’ and the remaining components are ‘0’.The knockdown precoding scheme having only the identity matrix as theuniversal matrix precodes an n^(th) column vector in the way of carryinga signal on an n^(th) transmit antenna without distortion and carryingno signal on the remaining transmit antennas. That is, in the knockdownmethod, the vector bitmap indicates which transmit antenna the knockdownmethod selects. For this reason, the knockdown precoding technique usingthe binary unitary precoding is called ‘Antenna Selection MIMO’.

Antenna Selection Space Time Transmit Diversity (STTD), like the AntennaSelection MIMO, is a technology that selects a transmit antenna andtransmits signals only via the selected antenna. However, while AntennaSelection MIMO has no limitation on the number of selected transmitantennas and sends signals of different MIMO layers via the selectedtransmit antennas separately, Antenna Selection STTD limits the numberof selected transmit antennas to 2, and applies STTD for signaltransmission using the two selected transmit antennas. STTD is designedto transmit one data stream with the Alamouti coding-based transmitdiversity technique. STTD is also called ‘orthogonal spatial coding’because it is characterized by arranging transmission complex symbols asshown in Equation (4) so that orthogonality between transmission symbolsmay be maintained in any space channel.

$\begin{matrix}\begin{bmatrix}S_{i} & {- S_{i + 1}^{*}} \\S_{i + 1} & S_{i}^{*}\end{bmatrix} & (4)\end{matrix}$

where S_(i) denotes an i^(th) symbol of a data stream. In the matrix ofEquation (4), rows are antenna dimensions and columns are timedimensions. That is, in a first symbol time, S_(i) is transmitted at afirst transmit antenna, and S_(i+1) is transmitted at a second transmitantenna in a second. In the next symbol time, −S_(i+1)* is transmittedat the first transmit antenna, and S_(i)* is transmitted at the secondtransmit antenna. In this manner, STTD forms the symbol matrix ofEquation (4) in the space and time. Because the OFDM system can transmitdifferent symbols not only in the time but also in the frequency, thecolumns can be frequency dimensions in the matrix of Equation (4).

FIG. 3 illustrates a structure of a transceiver employing AntennaSelection STTD, according to an embodiment of the present invention. Adesired transmission data stream is converted into one coded packetsignal stream after undergoing a channel coding and modulation processin block 101. This signal stream is converted into the form of signalstreams to be transmitted via two transmit antennas after undergoingSTTD coding in block 251. The transceiver performs Antenna Selectionprecoding in block 253 to realize Antenna Selection STTD. Herein,however, the number of selected antennas is 2. That is, the two spatialsignal streams generated by STTD coding in block 251 are transferred tothe selected two transmit antennas 109 a and 109 b via transmissionprocessors 107 a and 107 b, respectively.

The signals received at multiple receive antennas 111 a-111 n arecombined into one signal stream by a reception combiner 255 afterpassing through reception processors 113 a-113 n. This one signal streamis a signal obtained by linearly combining the STTD signal streamstransmitted from two transmit antennas. An STTD decoder 257 separatesthe signal streams combined in one signal stream using orthogonalitytherebetween. The separated signal streams are restored to thetransmission data stream by way of a demodulation and channel decoder119.

In the OFDMA system, a base station transmits pilots for synchronousdemodulation (or coherent detection) of forward transmission data andfor quality measurement of forward channels. The pilots used for datademodulation are classified into common pilots and dedicated pilotsaccording to their form.

The common pilot, a pilot transmitted by the base station, is commonlyused by several users (or terminals), and the common pilot can be usedfor both the data demodulation and the channel quality measurement. Thecommon pilot is characterized in that it always has the constant periodregardless of data transmission and resource assignment, and istransmitted over the entire available band of the system.

The dedicated pilot, a pilot transmitted to a particular user, is usedby one user, i.e., by only the user that receives data over a particularresource at a particular time. For the dedicated pilot, it is efficientto use the most preferred pattern according to the channel state for theuser occupying particular resources, and/or the Rank value for MIMOtransmission. For example, for a user in the frequency-selective fadingenvironment where the change in channel response is considerable in thefrequency domain, it is efficient to use the pilot pattern designed suchthat more pilots are inserted in the frequency domain; and for a user inthe fast fading environment where the change in channel response isconsiderable in the time domain, it is efficient to use the pilotpattern designed such that more pilots are inserted in the time domain.For the user with a Rank that will most likely be set as high, due to alow correlation between space channels and a larger number of receiveantennas, it is preferable to use the pilot pattern in which it ispossible to insert many orthogonal pilots used for distinguishinglayers. On the contrary, however, for the user with a Rank that willmost likely be set as low, it is preferable to use the pilot pattern inwhich it is possible to reduce the amount of resources to be assigned tothe pilot because there is no need to insert many orthogonal pilots.Therefore, for the dedicated pilot, the invention prepares multiplepatterns and selects the most appropriate pattern among them accordingto the channel state of the user.

The OFDMA system can be classified into: (i) a system that supports onlythe common pilot as a pilot for forward data demodulation; (ii) a systemthat supports only the dedicated pilot; and (iii) a system that supportsboth the common pilot and the dedicated pilot. Although the presentinvention will be described herein with reference to the systemsupporting both the common pilot and the dedicated pilot, the presentinvention can be used even for the system supporting only one of thecommon pilot and the dedicated pilot.

In the case where the base station uses the common pilot, when the basestation, in a process of transmitting forward data, intends to form oneor multiple beams by applying predetermined precoding for multipleantennas to transmit data over the beams, it is common that the basestation cannot apply precoding suitable for the particular user, to thecommon pilot. This is due to the fact that the common pilot is commonlyused for several users. Therefore, in the case where the base stationuses the common pilot and forms beam(s) by applying precoding for datatransmission to transmit data over the beams, the receiver, or terminal,for receiving the data should previously acquire information indicatingwhich precoding has been applied to the data transmission. This allowsthe receiver to perform channel estimation on the received common pilottaking into account the precoding applied to the data transmission, andthus enabling data demodulation.

However, in the case where the base station uses the dedicated pilot,when the base station, in a process of transmitting forward data,intends to form one or multiple beams by applying predeterminedprecoding for multiple antennas to transmit data over the beams, it iscommon that the base station applies the same precoding used for thedata transmission to the dedicated pilot before transmission. This ispossible because the dedicated pilot is a pilot only for one particularuser. The foregoing characteristic makes the receiver have no need forthe information indicating which precoding the transmitter has applied,in a process of receiving and demodulating the data to which precodingis applied. That is, because the same precoding was applied to the dataand the pilot, the data receiver only needs to perform channelestimation using the pilot, and as the channel estimation alreadyincludes the precoding, the receiver only needs to use the intactchannel estimated value for the data demodulation.

Using Table 2, a description will be made herein of fields of the sharedcontrol channel for MIMO transmission, which uses the foregoingprecoding and/or various types of dedicated pilot patterns.

Table 2 shows an message format of a shared control channel proposed bythe present invention. The present invention proposes to add a so-calledPilot/MIMO field. In the example of Table 2, an 8-bit Pilot/MIMO fieldis added. The 8 bits can be analyzed in different ways according to theuse/nonuse of the common pilot, the use/nonuse of the knockdownprecoding, and the use/nonuse of MCW MIMO. The numbers of bits, statedherein, are all given for convenience of description, and are subject tochange in actual realization.

TABLE 2 Field Block type MACID Persistent ChanID PF Ext. TX RankPilot/MIMO # bits 2 9-11 1 6-8 4-6 1 2 8 FLAM 00 1 1 1 1 1 0 0 MCW 01 11 1 1 1 0 1 FLAM1 MCW 10 1 0 0 3 1 0 1 FLAM2 SCW FLAM 11 1 1 1 1 1 1 1

When the common pilot is used, the pilot is not subject to precodingwhile the data signals are subject to precoding. Therefore, forestimation of an equivalent channel that has undergone precoding, it isnecessary to notify which precoding was used. Therefore, when the commonpilot is used, the Pilot/MIMO field is used as information for notifyingwhich precoding was used.

When the common pilot is used together with the knockdown precoding, thePilot/MIMO field is used as information for describing the knockdownprecoding scheme. In an MCW MIMO mode, only 1 bit among the 8 bits isused as a universal matrix index, and the remaining 7 bits are all setas a reversed value. In an SCW MIMO mode, 1 bit among the 8 bits is usedas a universal matrix index, 4 bits are used as a vector bitmap, and theremaining 3 bits are set as a reversed value. When there is only oneuniversal matrix, the 1 bit, which is set as the universal matrix index,is also set as the reversed value. The Antenna Selection MIMO techniqueis the typical knockdown precoding scheme that has only one universalmatrix.

When the common pilot is used together with the ready-made precoding,the Pilot/MIMO field is used as information for describing theready-made precoding scheme. In the MCW MIMO mode, 6 bits among the 8bits are used as a precoding matrix index, and the remaining 2 bits areall set as a reversed value. In the SCW MIMO mode, 6 bits among the 8bits are used as a precoding matrix index, and the remaining 2 bits areused as Rank information.

Because the dedicated pilot undergoes the same precoding as that for thedata, there is no need for the information for separately describing theprecoding scheme. Therefore, the Pilot/MIMO field is used as informationfor describing the pilot pattern and, when necessary, Rank. When thededicated pilot is used in the MCW MIMO mode, 2 bits among the 8 bitsare used as information for describing the pilot pattern, and theremaining 6 bits are set as a reversed value. When the dedicated pilotis used in the SCW MIMO mode, 2 bits among the 8 bits are used asinformation for describing the pilot pattern, 2 additional bits are usedas Rank information, and the remaining 4 bits are set as a reversedvalue.

Antenna Selection STTD can be supported only in the SCW MIMO mode, andcan be supported only when Antenna Selection precoding, i.e., binaryunitary precoding, among the knockdown precoding schemes is used.

When the common pilot is used together with the knockdown precoding, 1bit among the 8 bits of the Pilot/MIMO field is set as a universalmatrix index. However, when Antenna Selection MIMO is applied, it isprovided that the 1 bit is set as a reversed value because it ismeaningless. When it is intended to support Antenna Selection STTD, the1-bit universal matrix index, which is actually unused, is used forindicating whether the transmission is performed by Antenna SelectionSTTD. That is, the universal matrix index=1 indicates Antenna SelectionSTTD transmission, and the universal matrix index=0 indicates AntennaSelection MIMO transmission. In addition, the 4-bit vector bitmap isused for indicating selected antennas. Herein, when the number ofselected antennas is not 2, an error occurs. This is because STTD can beapplied only to two transmit antennas. The remaining 4 bits are set as areversed value.

When the dedicated pilot is used in the SCW MIMO mode, it is providedthat 2 bits among the 8 bits are used as information for describing thepilot pattern, and 2 bits are used as Rank information. In the AntennaSelection STTD technique, the Rank information is meaningless, becauseit is always that two transmit antennas should be selected and Rankis 1. Therefore, the 2 bits expected to be used as Rank information areset as a reversed value. Of the remaining 4 bits, 1 bit is used asinformation for indicating whether the transmission is performed byAntenna Selection STTD. In the Antenna Selection STTD and AntennaSelection MIMO operations, the dedicated pilot is a pilot of anassociated antenna, selected so as to estimate a channel of the selectedantenna. Therefore, the receiver does not need the process ofdetermining which antenna is selected.

With reference to the accompanying drawings, a description will now bemade of a method for writing (or recording) information messages in ashared control channel according to the present invention.

FIGS. 4 to 6 illustrate flowcharts in which a base station writes sharedcontrol channel information, according to an embodiment of the presentinvention. Referring to FIGS. 4 to 6, the base station determines instep 300 whether a common pilot is used or a dedicated pilot is used. Ifthe common pilot is used, the base station proceeds to step 310, and ifthe dedicated pilot is used, the base station proceeds to step 360 shownin FIG. 6.

If it is determined in step 300 that the common pilot is used, the basestation determines in step 310 whether it is in an MCW MIMO mode or anSCW MIMO mode. If it is in the MCW MIMO mode, the base stationdetermines in step 320 whether it uses knockdown precoding. However, ifit is in the SCW MIMO mode, the base station determines in step 321shown in FIG. 5 whether it uses knockdown precoding.

The base station operates as follows according to the use/nonuse of thecommon pilot in step 300, the selection of MCW MIMO or SCW MIMO mode instep 310, the use/nonuse of knockdown precoding in step 320, and theuse/nonuse of knockdown precoding in step 321 in FIG. 5.

When the base station uses the common pilot and the knockdown precodingin the MCW MIMO mode, the base station proceeds to step 322. When thebase station uses the common pilot and the ready-made precoding in theMCW MIMO mode, the base station proceeds to step 342. When the basestation uses the common pilot and the knockdown precoding in the SCWMIMO mode, the base station proceeds to step 330 in FIG. 5. When thebase station uses the common pilot and the ready-made precoding in theSCW MIMO mode, the base station proceeds to step 352 in FIG. 5.

When the base station uses the common pilot in the MCW MIMO mode whereit uses the knockdown precoding, the base station selects a particularknockdown precoding scheme and determines PFs of MCW MIMO in step 322.In step 324, the base station uses an MCW FLAM. In step 326, the basestation writes a universal matrix index in a Pilot/MIMO field, andwrites a PF associated with each layer in a PF field taking Rank intoaccount. In step 328, the base station writes the remaining MCW-FLAMfields.

When the base station uses the common pilot in the MCW MIMO mode whereit uses the ready-made precoding, the base station selects a particularready-made precoding scheme and determines PFs of MCW MIMO in step 342.In step 344, the base station uses an MCW FLAM. In step 346, the basestation writes a precoding matrix index in a Pilot/MIMO field, andwrites a PF associated with each layer in a PF field taking Rank intoaccount. In step 348, the base station writes the remaining MCW-FLAMfields.

When the base station uses the common pilot in the SCW MIMO mode whereit uses the ready-made precoding, the base station selects a particularready-made precoding scheme and determines a PF of SCW MIMO in step 352.In step 354, the base station uses an SCW FLAM. In step 356, the basestation writes a precoding matrix index and Rank in a Pilot/MIMO field,and writes the PF in a PF field. In step 358, the base station writesthe remaining SCW-FLAM fields.

When the base station uses the common pilot in the SCW MIMO mode whereit uses the knockdown precoding, the base station can use AntennaSelection STTD transmission only when the Antenna Selection precoding,i.e., binary unitary precoding, is used as the knockdown precoding.Therefore, the base station determines in step 330 whether thecorresponding transmission is Antenna Selection STTD transmission. Ifthe normal knockdown precoding is used for the transmission, the basestation proceeds to step 332, and if the corresponding transmission isAntenna Selection STTD transmission, the base station proceeds to step333.

When the base station uses the common pilot in the SCW MIMO mode whereit uses the normal knockdown precoding, the base station selects aparticular knockdown precoding scheme and determines a PF of SCW MIMO instep 332. In step 334, the base station uses an SCW FLAM. In step 336,the base station writes a universal matrix index and a vector bitmap ina Pilot/MIMO field, and writes the PF in a PF field. For AntennaSelection MIMO, the base station sets the universal matrix index to ‘0’in this step to distinguish Antenna Selection MIMO from AntennaSelection STTD. In step 338, the base station writes the remainingSCW-FLAM fields.

In the Antenna Selection STTD mode where the base station uses thecommon pilot, the base station selects two transmit antennas andcalculates a PF to be applied, in step 333. In step 335, the basestation uses an SCW FLAM. In step 337, the base station sets in aPilot/MIMO field a universal matrix index to ‘1’ to notify the AntennaSelection STTD mode and writes antenna selection information in a vectorbitmap, and writes the PF in a PF field. In step 339, the base stationwrites the remaining SCW-FLAM fields.

However, if it is determined in step 300 of FIG. 4 that the dedicatedpilot is used, the base station determines in step 360 of FIG. 6 whetherthe corresponding MIMO mode is an MCW MIMO mode or an SCW MIMO mode.

In the MCW MIMO mode where the base station uses the dedicated pilot,the base station selects a particular ready-made or knockdown precodingscheme, and determines PFs of MCW MIMO in step 362. In step 364, thebase station uses an MCW FLAM. In step 366, the base station writes apilot pattern in a Pilot/MIMO field and writes a PF associated with eachlayer in a PF field taking Rank into account. In step 368, the basestation writes the remaining MCW-FLAM fields.

In the SCW MIMO mode where the base station uses the dedicated pilot,Antenna Selection STTD transmission is available only when AntennaSelection precoding among the knockdown precoding schemes is used. If itis determined in step 370 that the corresponding transmission mode is anormal SCW MIMO mode, the base station proceeds to step 372, and if thecorresponding transmission mode is an Antenna Selection STTD mode, thebase station proceeds to step 373.

In the normal SCW MIMO mode where the base station uses the dedicatedpilot, the base station selects a particular ready-made or knockdownprecoding scheme and determines a PF of SCW MIMO in step 372. In step374, the base station uses an SCW FLAM. In step 376, the base stationwrites a pilot pattern and Rank in a Pilot/MIMO field, and writes the PFin a PF field taking Rank into account. In step 378, the base stationwrites the remaining SCW-FLAM fields.

Even in the Antenna Selection MIMO mode where the base station uses thededicated pilot, the base station performs steps 372 to 378. However, instep 376, the base station fills the bit indicating the AntennaSelection STTD mode in the Pilot/MIMO field with ‘0’ to clarify theAntenna Selection MIMO transmission.

In the Antenna Selection STTD mode where the base station uses thededicated pilot, the base station selects two transmit antennas andcalculates a PF in step 373. In step 375, the base station uses an SCWFLAM. In step 377, the base station sets, in a Pilot/MIMO field, anAntenna Selection STTD mode indication bit to ‘1’ to clarify the AntennaSelection STTD mode, writes a pilot pattern, and writes the PF in a PFfield taking Rank into account. In step 379, the base station writes theremaining SCW-FLAM fields.

FIGS. 7 to 10 illustrate flowcharts in which a terminal analyzes sharedcontrol channel information, according to an embodiment of the presentinvention. Referring to FIGS. 7 to 10, the terminal determines in step400 whether the common pilot is used or the dedicated pilot is used. Ifthe common pilot is used, the terminal proceeds to step 410, and if thededicated pilot is used, the terminal proceeds to step 411 shown in FIG.10.

When the common pilot is used, the terminal determines in step 410whether the corresponding MIMO mode is an MCW MIMO mode or an SCW MIMOmode. When the common pilot is used in the MCW MIMO mode, the terminalstarts MCW FLAM analysis from step 412, and when the common pilot isused in the SCW MIMO mode, the terminal starts SCW FLAM analysis fromstep 414 shown in FIG. 8.

When the common pilot is used in the MCW MIMO mode, the terminaldetermines in step 420 whether it uses knockdown precoding or ready-madeprecoding. When the terminal uses the common pilot in the MCW MIMO modewhere it uses the knockdown precoding, the terminal acquires a universalmatrix index from a Pilot/MIMO field and acquires Rank and PFinformation associated with each layer from a PF field in step 422. Whenthe terminal uses the common pilot in the MCW MIMO mode where it usesthe ready-made precoding, the terminal acquires a precoding matrix indexfrom a Pilot/MIMO field and acquires Rank and PF information associatedwith each layer from a PF field in step 424. Thereafter, in step 426,the terminal analyzes the remaining fields of the MCW FLAM. In step 428,the terminal determines both the precoding scheme and the MCW MIMO PF,and performs an MCW MIMO reception process based thereon.

When the common pilot is used in the SCW MIMO mode, the terminaldetermines in step 430 whether it uses knockdown precoding or ready-madeprecoding. If the terminal uses the knockdown precoding, the terminalfurther determines in step 440 whether it selects an Antenna Selectionprecoder.

When the terminal uses the common pilot in the SCW MIMO mode where ituses the ready-made precoding, the terminal acquires precoding matrixindex and Rank information from a Pilot/MIMO field, and acquires PFinformation from a PF field in step 432. When the terminal uses thecommon pilot in the SCW MIMO mode where it uses the knockdown precodingother than the Antenna Selection precoding, the terminal acquiresuniversal matrix index and vector bitmap information from a Pilot/MIMOfield and acquires PF information from a PF field in step 442.Thereafter, in step 436, the terminal analyzes the remaining fields ofthe SCW FLAM. In step 438, the terminal determines both the precodingscheme and the SCW MIMO PF and performs a SCW MIMO reception processbased thereon.

When terminal uses the common pilot in the SCW MIMO mode where it usesthe Antenna Selection precoding, the terminal acquires Antenna SelectionSTTD mode information from a universal matrix index in a Pilot/MIMOfield in step 444 shown in FIG. 9. In step 450, the terminal determinesbased on the information acquired in step 444 whether the correspondingtransmission is Antenna Selection STTD transmission or Antenna SelectionMIMO transmission. The universal matrix index=0 indicates AntennaSelection MIMO transmission and the universal matrix index=1 indicatesAntenna Selection STTD transmission. If it is determined that thecorresponding transmission is Antenna Selection SCW MIMO transmissionwhere the common pilot is used, the terminal proceeds to step 452.However, if it is determined that the corresponding transmission isAntenna Selection STTD transmission where the common pilot is used, theterminal proceeds to step 454.

When the terminal uses the common pilot for Antenna Selection SCW MIMOtransmission, the terminal analyzes antenna selection information from avector bitmap in a Pilot/MIMO field and acquires PF information from aPF field in step 452. In step 456, the terminal acquires information ofthe remaining fields in the SCW FLAM. In step 458, the terminaldetermines the selected antennas and PF, and performs SCW MIMO receptionbased thereon.

When the terminal uses the common pilot for Antenna Selection STTDtransmission, the terminal acquires antenna selection information from avector bitmap of a Pilot/MIMO field in step 454. Based on the vectorbitmap, the terminal can determine via which transmit antenna the actualtransmission has been achieved. In step 460, the terminal determineswhether the number of selected antennas is 2. Because Antenna SelectionSTTD selects two antennas for signal transmission, if the number ofselected transmit antennas is not 2, an operation error occurs.Therefore, if the number of selected antennas is not 2, the terminalends the reception process in step 462, determining that thecorresponding SCW FLAM is a wrong SCW FLAM. However, if the number ofselected antennas is 2, which is the information indicating the normalAntenna Selection STTD operation, the terminal acquires PF informationfrom a PF field in step 464. In step 466, the terminal acquiresinformation of the remaining fields in the SCW FLAM. In step 468, theterminal performs STTD decoding based on the antenna selectioninformation acquired in step 454 and the PF information acquired in step464.

However, if it is determined in step 400 of FIG. 7 that the dedicatedpilot is used, the terminal determines in step 411 of FIG. 10 whetherthe corresponding MIMO mode is the MCW MIMO mode or the SCW MIMO mode.

In the MCW MIMO mode where the terminal uses the dedicated pilot, theterminal starts analysis of MCW FLAM in step 416. In step 472, theterminal acquires pilot pattern information from a Pilot/MIMO field andacquires Rank and PF information associated with each layer from a PFfield. In step 476, the terminal acquires information of the remainingMCW FLAM fields. Thereafter, in step 478, the terminal determines whichpilot pattern and MCW MIMO PF it will use, and performs MCW MIMOreception based thereon.

In the SCW MIMO mode where the terminal uses the dedicated pilot, theterminal starts analysis of SCW FLAM in step 418. The terminaldetermines in step 480 whether it uses Antenna Selection precoding. Ifthe terminal uses the Antenna Selection precoding, the terminal proceedsto step 481, and if the terminal uses non-Antenna Selection precoding,the terminal proceeds to step 482 where it acquires pilot pattern andRank information from a Pilot/MIMO field and acquires PF informationfrom a PF field. In step 484, the terminal acquires information of theremaining fields in the SCW FLAM. In step 486, the terminal performs SCWMIMO reception based on the pilot pattern, PF, and Rank information.

When the terminal uses the dedicated pilot and the Antenna Selectionprecoding, the terminal acquires in step 481 the information indicatingwhether the corresponding transmission is Antenna Selection STTDtransmission or Antenna Selection precoding MIMO transmission, from theAntenna Selection STTD transmission bit in a Pilot/MIMO field.Thereafter, in step 490, the terminal determines whether thecorresponding transmission is Antenna Selection STTD transmission. Ifthe Antenna Selection STTD transmission bit is ‘1’, it indicates AntennaSelection STTD transmission, and if the Antenna Selection STTDtransmission bit is ‘0’, it indicates Antenna Selection precoding MIMOtransmission. When the corresponding transmission is Antenna SelectionSCW MIMO transmission where the dedicated pilot is used, the terminalproceeds to step 492, and when the corresponding transmission is AntennaSelection STTD transmission where the dedicated pilot is used, theterminal proceeds to step 491.

When the corresponding transmission is Antenna Selection SCW MIMOtransmission where the dedicated pilot is used, the terminal analyzes apilot pattern and Rank from a Pilot/MIMO field and analyzes a PF from aPF field in step 492. In step 496, the terminal acquires information ofthe remaining fields in the SCW FLAM. Thereafter, in step 498, theterminal performs Antenna Selection SCW MIMO reception using the pilotpattern, SCW PF, and Rank.

When the corresponding transmission is Antenna Selection STTDtransmission where the dedicated pilot is used, the terminal acquirespilot pattern information from a Pilot/MIMO field and acquires PFinformation from a PF field in step 491. In step 495, the terminalacquires information of the remaining fields in the SCW FLAM. In step497, the terminal performs STTD decoding based on the pilot pattern andthe PF information.

The foregoing embodiment secures 8 bits in the Pilot/MIMO field anddescribes how they are analyzed in several situations. The 8-bitinformation is needed is because 8 bits are required for notifying Rankwhile using the ready-made precoding. The ready-made precoding scheme islower than the knockdown precoding scheme in terms of the freedom degreefor column vector selection, so it needs to secure more precodingmatrixes. Therefore, a large amount of information is assigned to theprecoding matrix index. To reduce the number of bits secured for thePilot/MIMO field, the following embodiments can be used.

A first embodiment assigns only 6 bits to the Pilot/MIMO field. There isno difference in the Pilot/MIMO field using method between thisembodiment and the embodiment described in Table 2, except for the MIMOoperation of using the common pilot and the ready-made precoding scheme.However, when the common pilot is used together with the ready-madeprecoding scheme, the Pilot/MIMO field is used only as the precodingmatrix index. In this case, there is no space in which Rank informationis written in an operation of the SCW MIMO mode. When the common pilotis used together with the ready-made precoding scheme, it is possible inthe SCW MIMO mode to reduce the 2 bits to be used for Rank, by applyingthe restriction of using the Rank last reported by the terminal, insteadof not writing Rank. With the introduction of the restriction, the basestation can freely change the ready-made precoding scheme though itcannot perform MIMO transmission corresponding to the Rank value otherthan the Rank requested by the terminal.

A second embodiment assigns only 5 bits for the Pilot/MIMO field. Thereis no difference in the Pilot/MIMO field using method between thisembodiment and the embodiment described in Table 2, except for the MIMOoperation of using the common pilot and the ready-made precoding scheme.However, when the common pilot is used together with the ready-madeprecoding scheme, the Pilot/MIMO field is used only as the Rankinformation. That is, in the MCW MIMO mode, this embodiment sets all of5 bits as a reversed value without separately notifying a particularprecoding matrix. However, the embodiment applies the restriction ofusing the precoding matrix last reported by the terminal. Even in theSCW MIMO mode, the embodiment uses the 2 bits for Rank designationwithout separately notifying a particular precoding matrix, and sets theremaining 3 bits as a reversed value. Even in the SCW MIMO mode, theembodiment applies the restriction of using the precoding matrix lastreported by the terminal. With the introduction of the restriction, thebase station can apply a different Rank value from the value requestedby the terminal though it cannot apply the precoding scheme other thanthe precoding requested by the terminal.

When 5 bits are assigned for the Pilot/MIMO field and the common pilotis used together with the ready-made precoding scheme as in the secondembodiment, a further embodiment of setting the 5 bits as a reversedvalue regardless of the MCW MIMO mode or the SCW MIMO mode can beconsidered if the restriction based on the precoding and Rank requestedby the terminal is introduced unconditionally.

With the introduction of the restriction in which the base station usesthe intact MIMO-related information reported from the terminal as in thealternative embodiment, it is possible to efficiently reduce the amountof information in the Pilot/MIMO field. However, if the base station hasfailed to successfully receive the feedback information even though theterminal sent a request for a particular MIMO operation, the foregoingrestriction cannot be applied. In this case, it is possible to solve theproblem by switching to the transmit diversity or Single Input SingleOutput (SISO) transmission without applying the MCW MIMO or SCW MIMOtransmission.

Even in the alternative embodiment, the information indicating theAntenna Selection STTD transmission can be inserted. When the commonpilot is used, the universal matrix index, unused only for the SCW MIMOwhere Antenna Selection precoding is used, can be used as AntennaSelection STTD mode information. In the case where the dedicated pilotis used, if the 2-bit information indicating a pilot format and the2-bit information indicating Rank are excluded, the first anotherembodiment has 2 spare bits and the second another embodiment has 1spare bit. Of the spare bits, one bit is defined as Antenna SelectionSTTD mode information.

As is apparent from the forgoing description, the present invention canperform precoding using the message of the shared control channel and/orcan deliver various types of pilot pattern information. Therefore, whenthe common pilot is used, the invention can notify which precoding isused, and when the dedicated pilot is used, the invention can notifywhich pilot pattern is used. In addition, the present invention canindicate the Antenna Selection STTD transmission in an external wayusing the message of the shared control channel. Such informationtransmission facilitates capacity improvement and efficient resourcemanagement.

While the invention has been shown and described with reference to acertain preferred embodiment thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims.

What is claimed is:
 1. A method for receiving control information by aterminal, the method comprising: receiving a control channel message ona control channel; and extracting control information comprising atransmission rank and precoding matrix information from the controlchannel message if a common pilot is used for data demodulation, andextracting the control information comprising the transmission rank andinformation about a dedicated pilot from the control channel message ifthe dedicated pilot is used for the data demodulation.